There is a known vehicular impact absorber including (a) a hollow tubular body having a plurality of flat plate-shaped side walls and having a polygonal section, and (b) a vehicle body-side attachment plate that is fixed integrally with the tubular body via a bracket in a state where the vehicle body-side attachment plate is in contact with one axial end portion of the tubular body, (c) the vehicular impact absorber being fixed at the vehicle body-side attachment plate to a vehicle body-side member, and the vehicular impact absorber absorbing impact energy as the tubular body is crushed in the axial direction when an impact load is applied to the tubular body through the other axial end portion of the tubular body. A vehicular impact absorber illustrated in FIG. 12(a) in Patent Document 1 is an example of the above-described vehicular impact absorber, and a plurality of side walls of a tubular body is fixed with the use of a plurality of brackets bent into an L-shape. Further, FIG. 5 in Patent Document 2 illustrates a technique for fitting and joining an outer member having a rectangular tubular shape onto the outer side of a tubular body.